The invention relates to a process for preserving insulin-secreting cells intended to be transplanted in a patient.
The invention applies to the field of cell therapy for diabetes, which aims to prepare pancreatic islets or islets of Langerhans from pancreases obtained from brain-dead donors. These islets, which include insulin-secreting beta cells are then reinjected into the portal vein of a receiving patient in order to restore this patient's glycemia regulation without the use of daily recombinant insulin injections.
This cell therapy is therefore a beneficial alternative to pancreas transplant, with an easier surgery and fewer complications.
In practice, the pancreatic islets are isolated by enzymatic and mechanical digestion from a donor pancreas, then purified by density gradient. The islets are then perfused directly into the patient or cultivated for 1 to 3 days before transplantation.
This pre-transplantation culture or preservation step has proven to be beneficial at the metabolic and immunologic levels. Indeed, the time spent cultivating the islets can enable the transplant recipient to be prepared. In addition, this culture step enables the necessary quality controls to be performed on the islets before their perfusion.
However, with the current static preservation processes, between 40 and 60% of islets are lost during the first 24-hour period of culture after isolation.
In addition, the islets are cultured in an open environment in standard containers (flasks or Petri dishes) with numerous handlings, leading to a risk of viral or bacterial contamination of the islets.
Numerous studies have been conducted on the composition of the culture medium in order to improve the preservation of the islets in culture.
For example, document WO 2005/120576 proposes adding 50 M of alpha-tocopherol to a culture medium in order to reduce the damage caused to the pancreatic islets by anoxia. Document US 2007/0196810 proposes adding a polymerized hemoglobin to the culture medium used to isolate the pancreas islets. And, in the document US 2006/0246582, a laminin A chain peptide analog is added to the islet culture medium in order to enable the islet culture density to be increased to up to 300 islets/mL.
These media however remain insufficient for obtaining an acceptable survival rate of the islets in culture.
Regarding the conditioning of the islets, it was envisaged in documents EP-A1-1875802 and US 2005/0032205 to use a flexible pouch permeable to oxygen to cultivate the islets. The survival rate of the islets in these flexible pouches also remains insufficient.